Both Canon G1 X III and Ricoh GR IIIx have APS-C sized 24.0 MP resolution sensors so sensor size and resolution is not a differentiator between these two cameras.
One other difference between these two cameras that is worth mentioning is that Ricoh GR IIIx's sensor doesn't have an anti-alias (Low-Pass) filter. Removing anti-alias filter increases the sharpness and level of detail but at the same time, it increases the chance of moiré occurring in certain scenes.
Below you can see the G1 X III and GR IIIx sensor size comparison.
Sensor Size and Resolution Comparison image of Canon G1 X III and Ricoh GR IIIx Cameras
As seen above, Ricoh GR IIIx has a 1.1x Larger sensor area than Canon G1 X III. Larger sensors give photographer more control on the depth of field and blurry background compared to smaller sensor when shot in same focal length and aperture.
Sensor size sets the circle of confusion, so it drives how much depth of field each
of these bodies gives you at a given aperture. You can calculate it exactly for the
Canon G1 X III
or the
Ricoh GR IIIx ,
including hyperfocal distance.
